dictyNews Electronic Edition Volume 37, number 7 September 16, 2011 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= The induction of autophagy by mechanical stress Jason S. King*, Douwe M. Veltman and Robert H. Insall Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Bearsden, Glasgow. G61 1BD Autophagy, In Press The ability to respond and adapt to changes in the physical environment is a universal and essential cellular property. Here we demonstrate that cells respond to mechanical compressive stress by rapidly inducing autophagosome formation. We measure this response in both Dictyostelium and mammalian cells, indicating that this is an evolutionarily conserved, general response to mechanical stress. In Dictyostelium, the number of autophagosomes increases 20 fold within 10 minutes of 1kPa pressure being applied and a similar response is seen in mammalian cells after 30 minutes. We show in both cell types that autophagy is highly sensitive to changes in mechanical pressure and the response is graduated, with a half-maximal responses at ~0.2kPa, similar to other mechano-sensitive responses. We further show that the mechanical induction of autophagy is TOR-independent and transient, lasting until the cells adapt to their new environment and recover their shape. The autophagic response is therefore part of an integrated response to mechanical challenge, allowing cells to cope with a continuously changing physical environment. Submitted by: Jason King [j.king@beatson.gla.ac.uk] -------------------------------------------------------------------------------- Dictyostelium discoideum nucleoside diphosphate kinase C plays a negative regulatory role in phagocytosis, macropinocytosis and exocytosis. Sarah J. Annesley, Ruzica Bago, Maja Herak Bosnar, Vedrana Filic, Maja Marinovic, Igor Weber, Anil Mehta and Paul R. Fisher. PLoS One, accepted Nucleoside diphosphate kinases (NDPKs) are ubiquitous phosphotransfer enzymes responsible for producing most of the nucleoside triphosphates except for ATP. This role is important for the synthesis of nucleic acids and proteins and the metabolism of sugars and lipids. Apart from this housekeeping role NDPKs have been shown to have many regulatory functions in diverse cellular processes including proliferation and endocytosis. Although the protein has been shown to have a positive regulatory role in clathrin- and dynamin- mediated micropinocytosis, its roles in macropinocytosis and phagocytosis have not been studied. The additional non-housekeeping roles of NDPK are often independent of enzyme activity but dependent on the expression level of the protein. In this study we altered the expression level of NDPK in the model eukaryotic organism Dictyostelium discoideum through antisense inhibition and overexpression. We demonstrate that NDPK levels affect growth, endocytosis and exocytosis. In particular we find that Dictyostelium NDPK negatively regulates endocytosis in contrast to the positive regulatory role identified in higher eukaryotes. This can be explained by the differences in types of endocytosis that have been studied in the different systems - phagocytosis and macropinocytosis in Dictyostelium compared with micropinocytosis in mammalian cells. This is the first report of a role for NDPK in regulating macropinocytosis and phagocytosis, the former being the major fluid phase uptake mechanism for macrophages, dendritic cells and other (non dendritic) cells exposed to growth factors. Submitted by: Paul Fisher [P.Fisher@latrobe.edu.au] ============================================================== [End dictyNews, volume 37, number 7]